In spite of the general use of insulin, since its discovery more than 50 years ago, diabetes and its associated problems are still a major concern in world health. It is recognized that insulin, when injected, is only a treatment for certain facets of the disease and not a cure. Whilst millions of diabetics have been able to live normal lives, with greatly increased life spans, there are still complications of the disease, such as renal, cerebral and cardiovascular problems that are not controlled by the daily injection of the hormone. The intermittent administration of insulin and its release on a continuing basis, from Lente type materials, rather than the on-off response to physiological demand, such as is experienced with competent Islets of Langerhans, are thought to be responsible for the failure of insulin to control the complications of the disease. This seems to be especially true of the early onset diabetic, where the islets play unknown roles in the metabolism of vascular and neural tissues. In addition, it is known that 5 to 10% of diabetics develop resistance to the injected insulin and require ever increasing doses to maintain a controlled status.
Since the advent of transplantation surgery and its associated techniques, it would seem that diabetes might be cured, rather than treated, by the transplantation of pancreatic tissue from a donor. As with any transplantation technique, the surgeon is faced with rejection problems and accurate blood typing is required. It is apparent from information accumulated over the years, that different organs have different degrees of rejection associated with them. Drugs are needed, in any organ transplant, to suppress the antibodies formed by the host to the foreign implanted tissue, but also suppress immunity to common diseases and infections. From the limited data available, it is apparent that even with maximum care, transplantation of the pancreas is subject to even greater rejection problems than heart transplants. Data indicate that there has been no successful pancreatic transplant to date, maximum survival times being less than a year.
Attempts have been made to devise artificial pancreas which by monitoring glucose levels continuously and releasing insulin on demand keep the diabetic controlled in several aspects. One method requires the use of fast analytical techniques to determine the glucose level. This analysis has to be automatic and the results transferable to a mechanical means of adding insulin to the circulatory system to keep glucose levels within normal limits. Such a method is being used for those diabetics who are called "brittle", that is their daily insulin requirements are such that the balance between too high a glucose level and too high an insulin level is very difficult to maintain with an ordinary injection regime. Because of the associated assay equipment, the type of device used to carry out this method is large and the patient involved is permanently bedridden beside the apparatus. Even with present day miniaturization, it seems unlikely that such an instrument can be readily reduced to a portable machine.
A logical extension of the above techniques would be an artificial pancreas utilizing living tissue, that would not involve rejection phenomena, and would supply insulin to the patient depending on the circulating blood sugar levels as determined by biochemical reactions, rather than by mechanical means. One artificial endocrine pancreas is described in U.S. Pat. No. 3,827,565 issued Aug. 6, 1974 to Kenneth N. Matsumura and includes a flat membrane positioned in contact on one side thereof with the body fluid to be treated and on the opposite side thereof with live pancreatic islet cells. In addition to doubts whether the device has ever been used clinically, there is the further doubt of its operation since it is well known that if blood flows over a flat surface it is proned to coagulation.